Experiences with novel developed secondary conductivity sensors … · Experiences with novel developed secondary conductivity sensors within the German Calibration Service (DKD)

Experiences with novel developedsecondary conductivity sensors within the

German Calibration Service (DKD)

Ulrich Breuel Ulrich Breuel 11, Barbara Werner , Barbara Werner 22, Petra Spitzer , Petra Spitzer 33, Hans D. Jensen , Hans D. Jensen 44

1,21,2 Zentrum für Messen und Kalibrieren -ANALYTIK- GmbH, D-06766 Wolfen, Germany Zentrum für Messen und Kalibrieren -ANALYTIK- GmbH, D-06766 Wolfen, Germany

33 Physikalisch-Technische Bundesanstalt, D-38116 Braunschweig, Germany Physikalisch-Technische Bundesanstalt, D-38116 Braunschweig, Germany

44 Danish Institute of Fundamental Metrology, DK-2800 Kgs. Lyngby, Denmark Danish Institute of Fundamental Metrology, DK-2800 Kgs. Lyngby, Denmark

230th PTB Seminar Conductivity and salinity - Leitfähigkeit und Salinität PTB Braunschweig, September 13/14 2007

230th PTB Seminar Conductivity and salinity - Leitfähigkeit und Salinität 2

Agenda Introduction Introduction Measurement quantity Electrolytic ConductivityMeasurement quantity Electrolytic Conductivity Metrological hierarchy for Electrolytic ConductivityMetrological hierarchy for Electrolytic Conductivity NewNew ZMK development in detail ZMK development in detail Measurement of conductance Measurement of conductance GG Determination of the cell constantDetermination of the cell constant The measuring systemThe measuring system Temperature measurementTemperature measurement Cause and effect diagramCause and effect diagram Validation by means of intercomparisonsValidation by means of intercomparisons Summary and acknowledgementsSummary and acknowledgements


The ZMK group with the calibration laboratory -K-06901

Greatest number of quantities within a calibration laboratory

ZMK -ANALYTIK-

GmbH

Viscosity

Electrolytic conductivity

pH

Liquid density

Volume (Pipettes )

Electricity

Pressure

Mass

Balances

Torque

Time/frequency *

Temperature

Length equipment

Gauge blocks

Humidity

ZMK GmbH Sachsen-Anhalt

Ortsteil WolfenP-D ChemiePark Bitterfeld-WolfenAreal A; Filmstr. 7D-06766 Bitterfeld-WolfenGermany

Phone: +49 (3494) 6973 0Fax: +49 (3494) 6973 34E-Mail: [email protected]* Not accredited yet


The German Calibration Service (DKD)

Source: www.dkd.eu

Deutscher Kalibrierdienst

The DKD comprises calibration laboratories in industrial enterprises, research institutes, technical authorities, inspection and testing institutes. They are accredited and supervised by the Accreditation Body of the DKD and calibrate measuring instruments and material measures in the range and scope of accreditation.

Location of the ZMK Group


Quantity electrolytic conductivitywithin the NMI´s

Principle: Measurement of resistances in two different positions realized byPrinciple: Measurement of resistances in two different positions realized by

micropositioner systemmicropositioner system changing of center sectionschanging of center sections

Source: Primary methods for the measurement of electrolytic conductivity;

Accred. Qual. Assur (2003) 8:346-353


Quantity electrolytic conductivitywithin the DKD

Typical situation in the DKDTypical situation in the DKD

Measurement with commercial instruments and devices using 2- and 4-pole Measurement with commercial instruments and devices using 2- and 4-pole cells (same level as the users in the industry)cells (same level as the users in the industry)

Disadvantages:Disadvantages: Non-linearityNon-linearity Temperature compensationTemperature compensation Measuring uncertainties are too highMeasuring uncertainties are too high Dependence from the manufacturersDependence from the manufacturers


New standard cells by ZMK


Metrological hierarchy for electrolytic conductivity

Primary cells

Commercial measuring instruments and devices for

electrolytic conductivity

Reference standards (Standard cells)

Transfer standards:Certified reference solutionsfor electrolytic conductivity

Calibration objects

(of the nationalmetrological institutes )

Realized in the DKD by the results of the development project


New ZMK development in detail

Temperature independenceTemperature independence

Direct traceability to primary cellsDirect traceability to primary cells

Low measuring uncertaintiesLow measuring uncertainties

Manufacturer independenceManufacturer independence


New standard cell

Schematic image of a standard cell


Several types of cells needed?!

1.3 µS/cm 15 µS/cm 100 µS/cm 1 mS/cm 20 mS/cm

Deinionized water(appr. 1 µS/cm)

Rainwater(50 µS/cm)

Drinking water(500 µS/cm)

Industrial wastewater(5 mS/cm)

Seawater(50 mS/cm)

5 µS/cm …lowest value with

available reference solution in the DKD before finishing the

development project

Source of conductivity values: Principles of measuring technique, WTW GmbH


Extended measuring rangeby several cells

Cell A Cell B Cell E Cell C Cell D

4 mm

Platinization

Measuring Range

1.3 µS/cm 15 µS/cm 100 µS/cm 1 mS/cm 20 mS/cm

6 mm 20 mm 60 mm 60 mm


Standard cells

5 standard cells for different ranges of 5 standard cells for different ranges of electrolytic conductivity available (identified electrolytic conductivity available (identified with letters A to E)with letters A to E)

4 mm 60 mm

A D


Measurement of conductance G

BjGY ⋅+=

Real part … needed for determination of electrolytic conductivity

Conductance G in S

Imaginary part … not used

Susceptance B in S

Complex conductance Y in S

(1)

RG /1= (2)Ohmic resistance R in Ω


Example of G at different frequencies

Frequency range 0.5 to 5 kHz

y = -46.89x + 5.8656R2 = 0.9999

5,76

5,77

5,78

5,79

5,80

5,81

5,82

5,83

5,84

5,85

5,86

5,87

0,0000 0,0005 0,0010 0,0015 0,0020 0,0025

1/f in KHz-1

G in

mS

The conductance as a function of the reciprocal frequency


Determination of the cell constant

Frequency range 20 to 200 Hz

y = -1.7862x + 28.673R2 = 0.9976

28,57

28,58

28,59

28,60

28,61

28,62

28,63

28,64

28,65

28,66

28,67

0,0000 0,0100 0,0200 0,0300 0,0400 0,0500 0,0600

1/f in KHz-1

G in

µS

Example: determination of the cell constant of cell B

K = 0,1743 cm-1

Reference solution 5 µS/cm (nominal value), Hamilton Bonaduz AG, lot no. WO 12222520, certified by DFM (C0316)


Complete set-up for electrolytic conductivity determination

5 standard measuring cells5 standard measuring cells LCR-meter (Agilent 4284A)LCR-meter (Agilent 4284A) Precision thermostatic bath (oil bath, Precision thermostatic bath (oil bath,

Lauda Proline PV 36)Lauda Proline PV 36) Temperature measuring device Temperature measuring device

(temperature sensor Pt25 and (temperature sensor Pt25 and temperature indication instrument TTI-2)temperature indication instrument TTI-2)


Temperature measurement

Measuring electrodes of cell C and cell D

Spatial inhomogenity:

2 mK

Time stability:

3 mK

Temperature sensor:

Calibrated at temperature fixed points

Positions of the temperature sensors for the determination of spatial inhomogenity


Cause and effect diagram

Electrolytic conductivity

Cell constant

CO2 influence

CO2 Suppression factor

Conductance (LCR-Meter)

Drift of the reference cell

Bath homogenity

Conductivity reference cell

CO2 Equilibrium

CO2 Sensitivity coefficient

Temperature device

LCR-Meter

Conductance (LCR-Meter)

Extrapolation

Temperature coefficient

Temperature device

Temperature coefficient

Thermometer

Bath stability

Extrapolation

Repeatability


Validation by means of intercomparisons

2006

2005

2007

Intercomparison on electrolytic conductivity 2005 (5 µS/cm)

EUROMET Electrochemical Analysis WG Project 918; Study on the traceability of salinity measurements in seawater

Intercomparison on electrolytic conductivity 2007 (5 µS/cm)


Summary

Development of several standard cells Development of several standard cells with accommodation to defined with accommodation to defined measuring ranges is an improvement of measuring ranges is an improvement of the metrological traceability of electrolytic the metrological traceability of electrolytic conductivityconductivity

The aim – supply of reference solutions The aim – supply of reference solutions in the range from in the range from 1.3 µS/cm to > 100 1.3 µS/cm to > 100 mS/cmmS/cm is solved; national is solved; national

NewNew metrological metrological procedure is validatedprocedure is validated and active applied by ZMKand active applied by ZMK


Acknowledgements

We thank theWe thank theLandesförderinstitut Sachsen-AnhaltLandesförderinstitut Sachsen-Anhalt (Germany) (Germany)

for the financial support of the development for the financial support of the development project.project.

The authors would like to acknowledgeThe authors would like to acknowledgeDr. Reinhard LangeDr. Reinhard Lange and Mr. and Mr. Frank SeifertFrank Seifert

from Sensortechnik Meinsberg GmbH for their from Sensortechnik Meinsberg GmbH for their suggestions for the development of thesuggestions for the development of the

standard measuring cells.standard measuring cells.


Thank you for Thank you for your attention !your attention !

ZMK GmbH Sachsen-AnhaltZMK -ANALYTIK- GmbH

http:// www.zmk-wolfen.de


References

Guide to the Expression of Uncertainty in Measurement (GUM), 1st edition 1993,revision and restrike print 1995, International Organization for Standardization, Genf

9

K. Rommel, Leitfähigkeitsmessungen in Elektrolyten – Die Wahl der richtigen Frequenz, off print from the Fachzeitschrift für Labortechnik vol. 12, 1981

8

H.D. Jensen, N.-E. Dam, DFM measurement capability: Electrolytic conductivity – January 2005, DFM-report DFM-04-R81, Lyngby, 2005, pp. 1-7

7

H.D. Jensen, C. Verdier, Towards an improved primary standard for electrolytic conductivity, presentation of the Danish Institute of Fundamental Metrology at the NCSLI conference 2001

6

H.D. Jensen, J. Sørensen, Electrolytic conductivity at DFM – results and experiencesPTB-Bericht PTB-ThEx-15, Braunschweig, 2000, pp. 3-8

5

Y.C. Wu, W.F. Koch, K.W. Pratt, Proposed new electrolytic conductivity primary standards for KCl solutions, J. Res. Natl. Stand. Technol., vol 96, pp. 191-201, 1991

4

R.H. Shreiner, R.H., K.W. Pratt, Standard reference materials: Primary standards and standard reference materials for electrolytic conductivity, National Institute of Standards and Technology Special Publication, 2004, pp. 260-142

3

K.W. Pratt, W.F. Koch, Y.C. Wu, P.A. Berezansky, Molality-based primary standards of electrolytic conductivity, Pure App. Chem., vol. 73, no. 11, pp. 1783-1793, 2001

2

P. Spitzer, U. Sudmeier, U., Electrolytic conductivity – a new subject field at PTBPTB-report PTB-ThEx-15, PTB, Braunschweig, 2000, pp. 37-47

1

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Experiences with novel developed secondary conductivity sensors … · Experiences with novel developed secondary conductivity sensors within the German Calibration Service (DKD)